clock.h

[﹎不離。]

一个测定程序性能的问题
写一个计算多项式 a[0] + a[1] * x + ... + a[N–1] * xN–1
对不同长度的配列求出cycle count 再求出CPE值(cycle count 除以配列要素数？)

#include<stdio.h>
#include<stdlib.h>
#include "clock.h"

int fnx(int a[], int n, int x){
int i = 0, j = 0, num, fnx = 0;
int i_size = 1024;
int j_size = n / i_size;
for(i = 0; i < i_size; i++){
for(j = 0; j < j_size; j++){
num = i + j*i_size;
fnx += a[num] * x^(num);
}
}
for(i = i_size * j_size; i < n; i++){
fnx += a[i] * x^i;
}
return fnx;
}
int main(int argc, char *argv[]){
int i, n;
double d, error;
volatile int v;
n = atoi(argv[1]);
int *a = (int*)malloc(sizeof(int) * n);
for(i = 0; i < n; i++) a[i] = i;
start_counter();
error = get_counter();
start_counter();
v = fnx(a, n, 3);
d = get_counter();
d -= error;
printf("cycle num: %f\n", d);
printf("CPE: %f\n\n", d/n);
free(a);
return 0;
}

compile
gcc -Wall -O2 -I../include xxx.c ../lib/libcsapp32.a
时候出现
undefined reference to `_start_counter'
undefined reference to `_get_counter'
undefined reference to `_start_counter'
undefined reference to `_get_counter'
文件夹中有clock.h
是怎么回事呢

[赵4老师]

start_counter和get_counter函数的实现在哪里？